Electronic devices, for example electronic components or integrated circuits (ICs), are often transported in trays during production, whereby a single electronic device is packable in a single compartment (pocket) of the tray. Once the electronic devices are picked-up from the tray they are placed and packaged in compartments (pockets) of a tape. In particular, at least one electronic device is picked-up from a respective at least one compartment of the tray, transferred to a respective at least one compartment of a tape, and then placed into the respective at least one compartment of the tape. The steps of picking-up, transferring and placing are carried out by a pick and place device, whereby a single electronic device is packable in a single compartment of the tray or tape respectively. This process of transferring electronic devices from a tray to a tape is referred to as “taping a tray”. More generally, electronic devices are transferred from an input medium to an output medium. Hereby, “taping a tray” is only one possible type of transfer, the tray being the input medium and the tape being the output medium. In general, the input medium can be a tray or a tape, and the output medium can also be a tray or a tape. Even more generally, the input and output medium can be any kind of media or arrangement of compartments or pockets suitable for receiving, storing and containing electronic devices. In the following, the terms “compartment” and “pocket” are used in the same context, meaning any recess or opening in an upper side of the medium, the recess or opening being suitable for receiving, storing and containing an electronic device.
For example, the input medium and/or the output medium can be a JEDEC/EIAJ tray, i. e., built according to JEDEC (Joint Electron Devices Engineering Council) standard. In addition, the input medium and/or the output medium can be a molded matrix carrier for said electronic devices. A matrix with a plurality of compartments is formed in an upper side of the medium, so that a single compartment of the medium can receive and store at least a single electronic device. An X-Y coordinate system is assigned to the medium. A medium is defined by a theoretical model like a CAD (Computer Aided Design) data model which comprise target (theoretical) dimensions with tolerances: number of rows of compartments in the matrix, number of columns of compartments in the matrix, X- and Y-offset of the first compartment of the medium with respect to the edge of the medium, and pitch (dX, dY) between the compartments. However, the real dimensions of such a medium can vary over time, influenced by handling, temperature, batch or even supplier, etc.
For example, the input medium and/or the output medium can be a tape which is a flexible carrier with a linear array or a matrix of a plurality compartments for said electronic devices. Analogously to the tray; the same or another X-Y coordinate system is assigned to the tape, and the tape is defined by its CAD data which comprise target dimensions with tolerances: width, length, height, pitch, and F-value according to EIAJ (Electronic Industries Association of Japan) specification.
In order to place an electronic device correctly and well-aligned in a compartment of an output medium, the pick and place device has to                1) pick-up the electronic device from a defined known position on the electronic device, for example on the center of the electronic device, and        2) transfer and place the electronic device in a compartment of the output medium where the position of the compartment in the output medium and the dimensions of the electronic device have to be known.        
Ideally these positions can be taught once for all media of the same kind. In practice, however, there are several tolerances that require re-calibration. The two main tolerances are due to variations in handling and variations between media. By design, the latter tolerance is the more important one: media like trays can have variations of up to 1 mm. One of the reasons for these variations are that media are exposed to large temperature variations. They are heated up and cooled down while clamped on a holding device or stage.
Therefore, the general purpose is to re-calibrate the pick-up positions of a pick and place device for each new input medium such that the pick and place device can pick-up electronic devices from a defined known position on the electronic device placed in compartments of the respective input medium and then transfer the electronic devices to compartments in an output medium.
Depending on the required precision, two known different methods are used for solving above problem.
As to the first known method, in case the size of the compartment tolerance of the output medium (e. g., tape) is sufficiently larger than the compartment tolerance of the input medium (e. g., tray), only the fixed CAD data defined in the handler model is used. In this case, misalignment due to variations from one input medium to another is not an issue, because said sufficiently larger compartments of the output medium offer sufficient space for receiving and storing said relatively small electronic devices.
As to the second known method in the other case, if the difference between the size of the compartment and the size of the electronic device is small, precise alignment is required. This is done by visional alignment (VA) on electronic devices, i. e. mechanical alignment by using vision methodology on electronic devices. Here, the electronic device is picked-up from a compartment of the input medium and then transferred to a machine vision based inspection device in order to determine the position, or position data respectively, of the electronic device with respect to the pick and place device. This information is then used to align the electronic device correctly to a compartment of an output medium and drop or place the electronic device into said compartment of the output medium.
Often not only one but several electronic devices are simultaneously picked-up in parallel from parallel compartments of an input medium and simultaneously placed in parallel into parallel compartments of an output medium. Also here, VA is used to calculate an optimal correction such that no misplacement occurs.
While the VA approach is precise and reliable its disadvantage is that it is rather slow. Each electronic device needs to be transferred to an inspection device, or the inspection device needs to be transferred to the electronic device. Then the respective electronic device is measured there. Often not only one but several electronic devices are simultaneously transferred to an inspection device with a corresponding number of cameras (or to a corresponding number of inspection devices with a single camera respectively) and simultaneously inspected.
By VA inspecting the respective electronic devices of the respective medium in respective image fields of view of respective inspection device(s), actual, i. e., corrected, position data of the respective compartments of the input medium are determined before the respective electronic devices are placed in respective compartments of an output medium. However, inspecting each electronic device of the input medium extremely lengthens the process of transferring the electronic devices from the input medium to the output medium, particularly, if the throughout requirements of units (electronic devices) per hour are high, for example for throughout requirements of more than 20 000 units per hour.
In addition, VA disadvantageously does not guarantee a centered pick-up of the electronic device from the respective compartment of an input medium, whereby the term “centered pick-up” refers to the center of the respective compartment of the input medium.
Other effects, like when electronic devices are blown-off the center of the compartment of the input medium, have impact on the drop or placement behavior of electronic devices and may result in an inferior drop or placement in respective compartments of an output medium, i. e., in a higher possibility for misplacement of the electronic devices in the respective compartments of the output medium, even if an VA inspection has been carried out before.
With VA inspection the speed penalty becomes too large, even if the at least one inspection device is located near the input medium. However, without VA it is often hardly possible to use different input media without manually adjusting the CAD data of the input medium in the handler model (third method). The latter method has an even larger speed penalty.
For the moment there are two different techniques for the transfer of electronic devices from an input medium to an output medium:                1) blind transfers using only the CAD data of the input medium: This advantageously results in a basic flow of transfers and no speed penalty; however, blind transfers disadvantageously result in low precision and/or low complexity; and        2) VA: two-dimensional (2D) corrections and rotation correction for each electronic device separately, if necessary: This disadvantageously results in a slow or interrupted flow of transfers and high speed penalty; however, VA advantageously results in high complexity.        
Above term “complexity” refers to the density of packaged electronic devices, the smallness of compartments or electronic devices, respectively, and the number of compartments or electronic devices, respectively, in a medium. The smaller the electronic devices are and the denser the electronic devices are packed in correspondingly small and dense compartments of the medium, the higher is the number of electronic devices packable in the medium and the more complex are the medium dimensions and the requirements for a safe and precise pick-up, transfer and placement of the electronic devices.
In summary, advantages of the VA approach correspond with disadvantages of the blind transfer and adjusting-CAD-data approaches, whereas disadvantages of the VA approach correspond with advantages of the other said two approaches. Hence, there is a long-felt need to overcome, or at least reduce, the disadvantages of said three approaches.
U.S. Pat. No. 6,449,531 B1 discloses a method and an apparatus for transferring packaged integrated circuits from one JEDEC standard tray to another without manual handling of the ICs. Embodiments include a pick and place system for transferring ICs from a first tray to a second tray, motor drivers and a head for picking-up and placing the ICs by vacuum. The pick and place system is controlled by a processor that receives instructions from an input device. A first tray of ICs to be batched and a second tray to which the ICs are to be transferred are brought to the system. The operator enters data relating to the package to be transferred, the quantity of devices to be transferred, and the positions of the devices in the trays. The processor then controls the pick and place system to transfer the inputted quantity of devices from the first to the second tray based on the device positional information entered by the operator. Since there is no manual handling of the ICs, damage to the devices, such as bent leads, is eliminated, as is misorientation and miscounting of devices. Said method and said apparatus do not use VA and inspection devices.
U.S. patent application U.S. 2009/035119 A1 discloses a handling mechanism of trays with which electronic parts are fed and inspection device of the electronic parts using the mechanism. Through the provision of a tray placing rack for storing trays in multi steps, the trays accommodating electronic parts after inspection are received in the racks and through the provision of a tray stacking rack above the tray placing rack, an empty tray emptied by having been inspected of the electronic parts before inspection at an inspection stage is stacked on the tray stacking rack. When a certain tray is filled with electronic parts after inspection and is discharged, an empty tray is taken out from the tray stacking rack and the empty tray is fed to the rack position of the discharged tray to permit re-use of empty trays. Said method and said apparatus also do not use VA and inspection devices.